This invention relates to electronic digital computer systems and more particularly to a novel and improved associative crosspoint processor system operable on an associative search system.
Retrieving information from mass storage systems can be accomplished either by addressing specific locations in the mass memory or by serially searching each location for a specific content. The latter is usually accomplished by software using conventional hardware which is a software approach to content-addressing, or associativity. The so-called search-by-content method can also be accomplished by a hardware implementation of the associative memory. With this method externally applied information or data, which shall be referred to herein as key words, is compared to certain of the stored data or information in the mass memory. When the key data and stored data match, that stored data and any data associated therewith can then be retrieved.
In the prior art, in a rapid access associative memory, simultaneous comparisons are made bit-by-bit of every word stored in the memory against the contents of an interrogation register. A match signal identifies those words which compare with those words in the interrogation register.
Generally, an information retrieval system of this type is used in conjunction with a general-purpose digital computer which consists of a single central processing unit referred to herein as a CPU. A mass memory such as a magnetic memory disk is used and is capable of storing a very large amount of information for use in the CPU. Such memory disks normally access each track sequentially. Thus, to eliminate the need for supplying addresses to each block of stored data, the associative searching technique is employed.
Heretofore, searching systems have been devised whereby a bit-by-bit comparison of each word is performed by sequentially accessing each track from the disk into a comparison unit where each word on each track is compared bit-by-bit with the search word in a key register associated therewith. Such a system is shown and described in U.S. Pat. No. 3,435,423.
A feature of the present invention is that it improves on these prior art systems by making byte-by-byte comparisons of the information from the mass storage system with the key words in the key memories.
A further feature of the present invention is that it can operate on a variable-length textword base in the associative crosspoint processor as compared to fixed length words in the prior art system.
Yet a further feature of the present invention is that each comparison unit is operable with more than one key word in the associative searching system whereas prior art searching systems are operable on only a single key word.
Still another feature of the present invention is that this sytem is operable in conjunction with computer software available for controlling the associative searching system.